<template>
 <div>
    <span>全选:</span>
    <!-- 4. v-model 关联全选 - 选中状态 -->
    <input type="checkbox" v-model="num"/>
    <button @click="btn">反选</button>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        <!-- 3. 对象.c - 关联 选中状态 -->
        <input type="checkbox" v-model="item.c"/>
        <span>{{ item.name }}</span>
      </li>
    </ul>
  </div>
</template>

<script>

export default {
  data() {
    return {
      arr: [
        {
          name: "猪八戒",
          c: false,
        },
        {
          name: "孙悟空",
          c: false,
        },
        {
          name: "唐僧",
          c: false,
        },
        {
          name: "白龙马",
          c: false,
        },
      ],
    };
  },
  computed: {
    num:{
      get(){
        return  this.arr.every(item => item.c) 
      },
      set(val){
       return  this.arr.forEach( item => item.c = val);
      }
    }
  },
  methods: {
    btn(){
      return  this.arr.forEach(item => item.c = !item.c)
    }
  }
};
</script>